A variety of technologies have been studied and developed to suppress emissions (e.g., nitrogen oxide, hydrocarbon, and the like) by reducing heat of combustion in an internal combustion engine of a vehicle and to improve fuel efficiency by decreasing a mixture ratio between air and fuel.
Exhaust gas recirculation (EGR) systems, water injection systems, or the like have been studied and developed as a representative technology for reducing heat of combustion and nitrogen oxide and improving fuel efficiency.
A water injection system may inject water toward intake air or a fuel-air mixture or may directly inject water toward an intake port of an engine to lower the temperature of the engine, thereby reducing knocking and suppressing emissions, and may decrease a mixture ratio between air and fuel to increase engine power and torque.
However, if a flow rate decreases or droplets become larger in a specific part on account of flow characteristics in an intake pipe or manifold when a water injector injects water toward the intake port of the engine, insufficiently-gasified droplets may stagnate in the intake pipe or manifold, and the stagnant water may flow into the engine under a specific condition to cause an engine stall.
Furthermore, since the water injection system in the related art has to inject water more than 30% of average daily fuel consumption, a high-capacity water tank is required to store water, and therefore an installation space for an engine room may be limited.
The disclosure of this section is to provide background of the invention. Applicant notes that this section may contain information available before this application. However, by providing this section, Applicant does not admit that any information contained in this section constitutes prior art.